Saturday was a sad day for the ranks of Florida's zooists – people who have sex with other members of the animal kingdom. On 1 October, a state law went into effect that bars erotic contact between people and non-human animals, "however slight". The misdemeanor carries a jail sentence of up to one year.

Mention of bestiality typically elicits comedic cracks on hillbillies, polemics, as well as a resurgent intellectual interest in the topic. Turns out, there is a vocal contingent of bestiality enthusiasts. They think that human-animal eroticism is misunderstood, and decry both social and legal opposition to bestiality as a limitation of sexual freedom – unfair government intrusion into their bedroom (or barn) activities.

Just over a week ago, a dolphin-sex memoir surged in popularity. Malcolm Brenner, Wet Goddess author and bestiality advocate, wrote: "What is repulsive about a relationship where both partners feel and express love for each other?" Ethicist and animal rights activist Peter Singer got attention – and flak – for normalising bestiality in his 2001 essay "Heavy Petting". Cultural opposition to bestiality, he argued, is rooted in "speciesism". He argued that bestiality is moral so long as it's mutually pleasurable.

Bestiality critics advocate laws like Florida's for seemingly self-evident reasons – they think that bestiality is cruel, too perverse a kink to be legal. A handful of made-for-tabloid bestiality arrests easily supports this thesis: people rallied against a north Florida man who asphyxiated a pregnant goat during intercourse, even screen-printing "Baaa Means No!" T-shirts. Floridians were just as outraged by a blind man who routinely had sex with his guide dog, "Lucky". The prosecutor handling Lucky's case became so frustrated with Florida's weak animal welfare statutes that he virtually lobbied for the new law's passage.

Discussion of the mandate has tended to veer toward cheeky jokes, ignoring the fact that the measure provides the philosophic framework to protect human sexual rights and freedoms – even though it is a law regulating sex. Consider: one of the most basic tenets of sexual rights is that people should be allowed to indulge their weirdest and wildest curiosities and kinks without fear of reprisal – so as long the hookers, handcuffs, chains, latex, leather, whips etc with whatever gender, sex and number of people involved are being enjoyed by consenting adults in a private setting. Sexual rights also recognise the need for criminal and civil protections from people who don't play by the rules: that is, people who violate consent by forcing themselves on others.

Therefore, bestiality must be banned because it is a sexual act in which consent is impossible – animals cannot consent.

But wait, zooists will clamor! Animals can consent to sex with humans, and do so all the time – dolphins come on to swimmers by biting them, stallions fancy female riders with aggressive nuzzling and man's best friend, ever the leg-humper, would rather be friends with benefits. But such anecdotal "evidence" is rife with epistemic flaws, some of which are identified in Thomas Nagel's 1974 essay "What is it like to be a bat?"

To be clear, Nagel wasn't writing specifically about bestiality. He's arguing against reductionism – the idea that mind and experience can be understood with a straight-up, scientific analysis of various parts.

He proves his point by pointing out that humans cannot know what it is like to be a bat – the subjective experience of being a bat, that is – because there is far more to the picture than fluttering sightlessly around and jones-ing for flies. There is a phenomenology of bat-ness, Nagel argues, which we cannot understand by trying to piece together bats' inner lives from the outside.

Nagel's idea is integral in understanding animal consent. It seems pretty reasonable to say that we can't probably can't "get" the phenomenology of bats. It also seems pretty reasonable to say that we probably can't "get" the phenomenology of other animals – nothing really seems to suggest otherwise. Since consent appears to be an internal, phenomenological decision-making process, we probably can't "get" whether an animal grants it.

Zooists might counter that animals "consent" to human sex by physical gestures, but that's not convincing. Think about how confusingly body language plays out across human cultures – how a handshake could delight some and viciously offend others – and we are all using the same basic behavioral framework. Animals are even more different and confusing, and they are wired differently on top of that. So, for zooists to say that we can understand animals "body language" – to the point of acquiring sexual consent from them – is absurd.

A healthy, sex-positive society cannot allow sexual activity to occur in which clear consent is not present, even if the non-consenting party is not human. To do so would undermine the objective importance of consent. Laws barring bestiality, such as the one recently enacted in Florida, are not wrongful limitations of sexual freedom. They rightfully protect the sexual liberties of all.